Ph.D. Dissertation Defense by Michael Michaux
Wednesday, June 15, 2005

(Dr. Kenneth A. Cunefare, Chair)

"Suppression of Friction-Induced Oscillations through Use of High-Frequency Dither Signals"


Friction-induced oscillations occur in many engineering systems, often resulting in noise, vibration, and excessive or uneven wear. This proposal addresses the suppression of such oscillations, especially with application to braking systems, through the use of high-frequency dither signals. Brake squeal is an annoying and elusive problem too often present in braking systems of automobiles, trucks and aircraft.

In previous work, the effectiveness of high-frequency dither to eliminate squeal in an automotive disc brake assembly was demonstrated experimentally. The main features of the dither-squeal cancellation system was the application of a high frequency variation in the brake pressure force accomplished by means of a piezoelectric stack placed behind one of the brake pads.

The goal of this research is the understanding of the origin of brake squeal, and the effect of dither control. Using dither control as a mean for suppressing brake squeal requires the understanding of several different phenomena, such as friction, geometric instabilities and structural coupling. Characteristics of the dither signal itself will be investigated in order to determine which types of signals yield the best performances. Also considered, will be the orientation of the dither force input relative to the frictional contact plane. The effectiveness of dither inputs applied tangent to and normal to the plane of contact will be explored. Several types of brake-system models will be developed, each designed to test some aspect of the problem or to facilitate the application of analytical techniques.